The invention relates to a compressed air supply device for a utility vehicle, having a valve housing and having an air dryer cartridge which is releasably connected to the valve housing.
Compressed air supply devices of said type provide treated compressed air to compressed air consumers in utility vehicles. Typical compressed air consumers are for example a pneumatic brake system or an air suspension system. A compressed air supply device combines numerous functions. One important task is that of drying and cleaning the air. For this purpose, an air dryer cartridge is provided which contains filter devices and a drying agent. Other important tasks are those of regulating the pressure of the compressed air provided by a compressor and reliably distributing the compressed air between the different consumer circuits. Said tasks are performed by valve devices which are accommodated in a valve housing, specifically a pressure regulator and a multi-circuit protection valve. Modern compressed air supply devices comprise, in addition to the pneumatic components, an electronic controller and electrically actuable components, for example solenoid valves, and a sensor arrangement which is connected to the electronic controller. The compressed air supply devices which are equipped in this way are also referred to as EAC (Electronic Air Control) systems.
Since the absorption capacity of the air dryer cartridge for foreign substances and humidity is limited, said air dryer cartridge must be regenerated, and ultimately exchanged, at regular intervals and as a function of the delivery capacity of the compressor. It should expediently be possible for the servicing process of exchanging the air dryer cartridge to be carried out by the driver of the utility vehicle himself, that is to say without the aid of a workshop. Consequently, the air dryer cartridges are attached to the valve housing at an easily accessible location by means of a multi-start thread. If it is necessary for the driver of the utility vehicle to exchange the air dryer cartridge, then it is merely necessary here for the cartridge to be unscrewed, wherein during the unscrewing process, the residual pressure present in the compressed air system can escape without any problems. The new air dryer cartridge can then be connected to the valve housing by the thread.
One problem of the connection type by a thread is that the driver of the utility vehicle must have a sense of how tightly the air dryer cartridge should be screwed to the valve housing. Here, he may be assisted by means of a tool which is to be carried on-board and which always ensures correct assembly, wherein the carrying of the tool however then constitutes additional expenditure. Furthermore, a certain additional assembly height is required for the threaded connection, which counteracts the general desire to reduce the installation space of vehicle components.
The object on which the invention is based is that of providing a compressed air supply device which, while having a low assembly height, permits fault-free and reliable assembly of the air dryer cartridge, wherein in particular, no tools should be necessary.
The invention builds on the generic compressed air supply device in that the valve housing and the air dryer cartridge are connected to one another by means of a bayonet connection. A bayonet connection offers the advantage of an assembly height which is reduced in relation to that of a threaded connection, and the assembly of the air dryer cartridge is simplified in relation to the conventional assembly by means of a thread.
According to one preferred embodiment, it is provided that the air dryer cartridge and the valve housing have, at least in sections, in each case one substantially radially outwardly extending collar, with sections being formed by at least one of said collars, which sections have an axial collar thickness which increases in the closing direction of the bayonet connection, and in that an outer bayonet ring which is guided by means of the collars and which can be released from the air dryer cartridge and the valve housing is provided, which outer bayonet ring has a radially inwardly extending collar and, offset in the axial direction with respect thereto, inwardly directed projections, with the axial width of the projections being matched to the variable axial collar thickness in such a way that the bayonet connection can be closed or released by means of a relative rotation of the outer bayonet ring and the valve housing or air dryer cartridge respectively. An outer bayonet ring is expedient as a connecting element if the valve housing and the air dryer cartridge should have substantially the same radial dimensions.
It is expediently provided that the collar of the valve housing has a plurality of collar sections which extend in the tangential direction and which have an axial collar thickness which increases in the closing direction of the bayonet connection and recesses which are provided between said collar sections, and in that the collar of the air dryer cartridge extends substantially uniformly over the entire periphery and, when the bayonet connection is closed, interacts by means of a seal with the valve housing. The comparatively thin-walled air dryer cartridge therefore need not have any special design in the region of its collar, while the bevels required for realizing the bayonet connection are realized in the region of the valve housing.
It is preferable if the collar sections at least partially have a stop for limiting the closing rotation of the bayonet connection. As a result of the stop, there is no longer any doubt for the driver, when placing on a new air dryer cartridge, that assembly has been carried out correctly.
Furthermore, it can expediently be provided that the outer bayonet ring is rotationally secured with respect to the air dryer cartridge. Rotation of the air dryer cartridge in the sealed state via the sealing surface is thereby prevented.
According to a further preferred embodiment of the present invention, it is provided that the air dryer cartridge has a substantially radially outwardly extending collar which, in the closed state of the bayonet connection, can be acted on with a force in the axial direction by means of an inner bayonet ring which surrounds the air dryer cartridge, in that the inner bayonet ring has a radially outwardly extending collar and, offset in the axial direction with respect thereto, outwardly directed projections which have an axial projection thickness which increases in the closing direction of the bayonet connection, and in that a part, which is situated at least partially radially outside the inner bayonet ring, of the valve housing has radially outwardly extending recesses whose axial thicknesses are adapted to the projections of the valve housing in such a way that the bayonet connection can be closed or released by a relative rotation of the inner bayonet ring and the valve housing. The use of an inner bayonet ring is expedient if the valve housing has a larger radius than the air dryer cartridge. The inner bayonet ring is then inserted into the valve housing without taking up further installation space.
As already provided in the case of the outer bayonet ring, it is provided that the projections of the inner bayonet ring at least partially have a stop for limiting the closing rotation of the bayonet connection.
It may likewise be provided that the inner bayonet ring is rotationally secured with respect to the air dryer cartridge.
According to one preferred embodiment of the invention, it is provided that the inner bayonet ring can be released from the air dryer cartridge. This corresponds to the principle which is likewise realized in connection with the outer bayonet, in which the bayonet ring, as an additional component, generates the connection of the air dryer cartridge and valve housing.
Here, it may expediently be provided that the air dryer cartridge interacts with the valve housing via a seal when the bayonet connection is closed. In the case of a direct sealing connection of the air dryer cartridge and valve housing, this may be referred to as an open design of the air dryer cartridge, which is particularly expedient with regard to a reduction in structural height.
According to a further embodiment, it may however also be provided that the inner bayonet ring is fixedly connected to the air dryer cartridge and forms at least a part of a foot flange of the air dryer cartridge. A closed system of said type is advantageous in particular with regard to assembly, since only two components are involved.
According to a further particularly preferred embodiment of the compressed air supply device according to the invention, it is provided that the bayonet connection has a bayonet ring which has an opening which holds a securing element, with the securing element latching, in the closed state of the bayonet connection, into an opening of the valve housing, via which opening the compressed air supply device can be ventilated by means of an actuation of the securing element. In addition to the stops which are preferably provided in the bayonet connection and which limit the rotation of the bayonet connection, a latching securing element can offer additional security. The latching can be audibly perceived by the driver. Furthermore, the securing element makes it possible for the compressed air supply device to be ventilated before the opening of the bayonet connection. This is expedient in the case of a connection by a bayonet connection since, otherwise, an abrupt ventilation could take place after a slight opening movement of the bayonet connection, which could sometimes lead to dangerous situations. Since the securing element latches in the closed state of the bayonet connection and thereby prevents the opening movement, it is ensured that a ventilation must always take place, by the actuation of the securing element, before the opening process.
This is realized in structural terms in that the securing element has a lug which is pressed by the force of a spring into the opening of the valve housing, with the lug being movable counter to the spring force in order to ventilate the compressed air supply device and in order to enable the opening movement of the bayonet connection.
It may also be provided that the valve housing has an eccentric pin which projects in the direction of the air dryer cartridge and which protrudes into an opening of a drying agent box which is arranged in a housing of the air dryer cartridge, with the length of the pin being dimensioned such that the first contact between the air dryer cartridge and the valve housing during assembly takes place by said pin. The centering aid and rotational locking provided in this way are first made possible by means of the connection of the valve housing and air dryer cartridge by a bayonet connection, since in the case of a connection with a multi-start thread, a rotation of the air dryer cartridge and valve housing relative to one another is necessary.
The invention also relates to a valve housing for a compressed air supply device according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.